Getting Gcg Highflow To Hold Boost For Longer, 18psi To 15psi Drop By Redline

[Rolls]

I've got a highflowed rb20 turbo on my rb25, makes peak power of 236kw around 5000-6500rpm, drops off slightly to about 215kw by 7500rpm but the boost has dropped from a peak of 18psi around 4000rpm to ~15psi by late 6000 rpm.

Now I know the rear housing is massively undersized which is the cause, but I like it because it provides AMAZING response, comes on better than the stock turbo and the midrange is amazing.

Now I was wondering if I get a stronger/stiffer actuator arm, is it possible I could get the gate to stop blowing open in the top end? Or is this a fruitless exercise that will just result in my EGTs soaring and only a slight power increase?

Cheers

Edited October 4, 2010 by Rolls

[DVS JEZ]

What boost control are u using?

[Rolls]

What boost control are u using?

rb20 actuator which runs about 13psi to redline, then using an eboost street to get it up to 18, though no matter what tuning you do the boost level drops indicating its blowing the gate open, common problem with the highflows that use the smaller housings from what Ive read.

Would just get an actuator that ran 18psi but I like being able to turn it down to 13psi in the wet and when its 35c outside, motor can take it just makes me feel better.

[zebra]

what about a HKS 1bar adjustable item, could just wind a big whack of preload on it when you want big boost and loosen it off if you are doing a heap of wet driving.

[Rolls]

what about a HKS 1bar adjustable item, could just wind a big whack of preload on it when you want big boost and loosen it off if you are doing a heap of wet driving.

So you think this would help hold it open? Don't want to get it if I find I have to run so much preload to hold it closed that it spikes or runs 18 straight off the spring.

Will consider it though, you know how much something like that costs?

[zebra]

http://www.nengun.com/hks/heavy-duty-actuators

aboot 200 buckos from nengun, but you could probably get the same item from GCG without the HKS sticker for less.

you would just have to play with the preload until you have it where you want it.

[R31Nismoid]

RB25's have a issue with GCG hi-flows when using the factory actuator, you actually need to buy a heavy duty one and they are lazy up onto boost in a number of cases.

I feel GCG should MAKE people buy a new actuator as part of the purchase, but they don't and can lead to unhappy customers simply because they are uneducated... (unless its changed recently?)

Whilst the RB20 one holds a tad more standard, it is by no means a heavy duty one and i would be changing it by default were it my car.

[scotty nm35]

Rather than pay through the nose for an upgraded actuator, or cutting the original actuator apart to upgrade the spring, I decided to fit an external spring. I will let you know how it goes once its tuned...

Understand that increasing the pressure in the manifold causes the exhaust temps to rise, for street this may not be that much of a problem but an EGT gauge would be a good idea.

Im hoping the ethanol I run may help with the cooling, not just because of its properties but also there is much more of it spraying in. If this is the case, the EGT's shouldnt rise too much.

[hypergear]

Don't wast you money on the HKS actuator, Won't work. You need customized actuator with wastegate controller. Send the turbo in, We can make it hold as much boost as you want as you've seen on our results.

[Harey]

I have a similar problem except I have a big 0.82 exhaust housing that i know can hold 18psi flat. I am thinking mine could be restrictive catback exhaust, I am getting it tested today.

[joeyjoejoejuniorshabadoo]

Would just get an actuator that ran 18psi but I like being able to turn it down to 13psi in the wet and when its 35c outside, motor can take it just makes me feel better.

this i don't understand...

in the wet the only thing that controls the car is your right foot. i run 20psi all day every day and in the wet i just don't put my foot down as much as in the dry...

it's pretty simple really

[R31Nismoid]

^ Same - I ran 24psi/370rwkw on the street - controlled by the right foot.

Getting the actuator as close to the target boost is what you want.

None of this "hi/low" boost business.

[discopotato03]

If it were me I'd think about getting an RB25's turbine housing machined to suit the GCG Hi Flow because they are not too much larger than the RB20 one and I reckon taking a bit more of the restriction out of the hot side would pay off .

If you remember that RB20's were rated at about 160 Kw and R33 RB25's about 184 there isn't a whole lot of difference to raw power numbers .

From a turbine housing perspective the exhaust can only escape via the turbine outlet and the waste gates port , its not that easy to enlarge the gates hole significantly and even if you could the exhaust gas pressure and velocity works bloody hard to force the flap open .

Anyway as I said compare a 20 with a 25 (R33 spec) turbine housing because at a glance they look very similar size wise . The only reason I know they're different is because I stuck something down the throats of the two representing a go/no go gauge and proved the R33 25's one is slightly larger , slightly being the operative word because the difference is not huge v.

You also have the opportunity to play with compressor housings if doing just the turbine housing isn't enough . The RB25 and single BB turbo VG30 used a larger compressor housing and it bolts straight on once its machined to suit the compressor wheel . These housings have a smoother cast finish and have "Nissan" on them in bold block lettering . Aside from the BB VG30 turbo using a slightly smaller compressor wheel the only difference housing wise is that the RB25 ones have an anti reversion grove machined into the snout of them , same casting I reckon .

Anyway the RB20 compressor housing should give the best response because the smaller passage means higher velocity for a given wheel speed .

My 2c spent , cheers A .

Edited October 4, 2010 by discopotato03

[Harey]

^ Same - I ran 24psi/370rwkw on the street - controlled by the right foot.

Getting the actuator as close to the target boost is what you want.

None of this "hi/low" boost business.

Agree full throttle at 13psi is still going to cause you issues in the wet.

[NYTSKY]

None of this "hi/low" boost business.

There is a low boost???

[R31Nismoid]

^ Not in my neck of the woods there isn't lol

[BoostdR]

Don't wast you money on the HKS actuator, Won't work. You need customized actuator with wastegate controller. Send the turbo in, We can make it hold as much boost as you want as you've seen on our results.

I have seen the Gibson GTR wastegate setup. I has a Actuator with two feeds. One above the diaphram and one below to actually increase pressure as boost increases. They say it made all the difference.

Is this the mod you are mentioning...and can I get it done to my HKS GTRS's?

Matt

Edited October 4, 2010 by BoostdR

[hypergear]

I have seen the Gibson GTR wastegate setup. I has a Actuator with two feeds. One above the diaphram and one below to actually increase pressure as boost increases. They say it made all the difference.

Is this the mod you are mentioning...and can I get it done to my HKS GTRS's?

Matt

That doesn't work. I've tried it. because the exhaust manifold pressure is lot higher. Might work if you connect that into exhaust manifold, which will burn the diaphragm.

I've spent few weeks investigating this issue, I've tested every thing, and all it does is spiking boost. But on the end I've found a way to hold it, it works perfectly, and there is no other way that you can make it to work. I've managed to peak 297rwkws and consistent 273rwkws holding 20psi with the 2IU R33 turbine housing. link:

http://www.skylinesaustralia.com/forums/Ma...et-t338520.html

This also depending on they type of turbine wheel and housing profile method, above is very unique.

Plus I strongly advise to no run too much boost if you are running the Ball bearing XTR GCG high flow with Factory bearing housing. I had few sent in for repair, there is a weak bearing component (stock part) that fails under high back pressure.

[Rolls]

If it were me I'd think about getting an RB25's turbine housing machined to suit the GCG Hi Flow because they are not too much larger than the RB20 one and I reckon taking a bit more of the restriction out of the hot side would pay off

If I was going to go to the trouble of highflowing another turbo I would just go all out and get a garret turbo and manifold.

Plus I strongly advise to no run too much boost if you are running the Ball bearing XTR GCG high flow with Factory bearing housing. I had few sent in for repair, there is a weak bearing component (stock part) that fails under high back pressure.

What fails and around what mark? Do all of their highflows use the standard bearing housing? You mentioned in that thread that the entire rear housing was glowing red hot, surely this would not be good for the life of the bearing? The car is a daily driven street car mainly, but it does see some track time so it has to be reliable.

Don't wast you money on the HKS actuator, Won't work. You need customized actuator with wastegate controller. Send the turbo in, We can make it hold as much boost as you want as you've seen on our results.

The car is my daily driver so taking the turbo off and sending it in isn't really an option, I can live with less boost as it is still plenty of power, just wondering if there was a relatively simple way to get it to hold more, if the higher boost all the way is going to be detrimental to the bearings life like you mentioned then I probably don't want to do it anyway.

[Prue]

If I was going to go to the trouble of highflowing another turbo I would just go all out and get a garret turbo and manifold.

What fails and around what mark? Do all of their highflows use the standard bearing housing? You mentioned in that thread that the entire rear housing was glowing red hot, surely this would not be good for the life of the bearing? The car is a daily driven street car mainly, but it does see some track time so it has to be reliable.

The car is my daily driver so taking the turbo off and sending it in isn't really an option, I can live with less boost as it is still plenty of power, just wondering if there was a relatively simple way to get it to hold more, if the higher boost all the way is going to be detrimental to the bearings life like you mentioned then I probably don't want to do it anyway.

My very old mtq high flow held 20psi easily, using a standard rb25 actuator, and I wouldn't touch one of wastegate jammer/stopper things with a 10ft barge pole, what happens on a cold night where the gate flap needs to open more...it can't so hello mega over boost.

Rolls - do you run the boost line to the actuator from the intercooler piping or the plenum? If its off the cooler piping try running it off the plenum, worked for my car and works for every sr powered S13.

p.s its zebra...not Prue lol